The optical isolator is nonreciprocal optical devices with a dual port. The characteristics of optical isolator is positive: low insertion loss, high reverse isolation, high return loss. Optical isolator is allows light to a direction through and stop in the opposite direction to the passive devices, the role is to light the direction of restrictions, make light only one-way transmission, through optical fiber echo reflection can be optical isolator isolation, to improve the transmission efficiency of light. Its role is to prevent the light path due to various causes of the transmission of light to the light source and the adverse effects of the optical path system.